Changing deployment variable values through UI at runtime

The application uses a Configuration file , to decide on the paths to search for files on the server .

The Welcome page displays this information on the client side , allowing the user to change / edit or simply confirm the values .

For most of the times , it would be a simple confirm , but the edit and save options have been provided to be able to change these paths .

Now these values are read and set in a "ConfigObject - simply getters and setters" at servlet startup [ init method ] , kind of global variable . and this object is available to all requests .
There are two save options , that i intend to provide : a) Edit the values for this session / user only . So the User say changes a particular value and now the modified value is used for him .
b) Edit the values permanently : So say the path on the server changed . A normal way would be to change the values in the configuration file and then redeploy the application .
I want to ask , is it possible to change the values of a global variable at runtime and still it gets reflected for all new requests , without starting the server .